2-Chloro-1,1-difluoroethane (HCFC-142 or R142) is used as blowing agent in the manufacture of foams, or as raw material in the manufacture of pharmaceutical or agrochemical compounds.
2-Chloro-1,1-difluoroethane can be obtained by fluorination of 1,1,2-trichloroethane (T112). This fluorination reaction generates a by-product, trans-dichloroethylene (TDCE), in not insignificant quantities. In order to guarantee a satisfactory purity of the final product, the TDCE should be removed as completely as possible from the mixture obtained at the end of the reaction.
WO 2013/053800 describes a catalytic fluorination process of 1,1,2-trichloroethane and/or of 1,2-dichloro-ethene in the presence of HF in order to obtain 1-chloro-2,2-difluoroethane. This document describes a step wherein 1,2-dichloro-ethene and 1,1,2-trichloroethane are separated from 1-chloro-2,2-difluoroethane by distillation. This document does not describe the process according to the invention comprising a step of extractive distillation.
The existence of an azeotrope or quasi-azeotrope R142/TDCE makes the complete separation of the R142 and TDCE by simple distillation very difficult.